The long-term goal of this project is to elucidate the global structure and behavior of gene regulatory network in development and aging. To this end, we have been developing tools and resources that make it possible to analyze a large number of genes in various experimental conditions. In our earlier work, we 1) constructed cDNA libraries from early mouse embryos and stem cells and generated a large number of expressed sequence tags (ESTs), 2) developed a glass-slide microarray platform containing in situ-synthesized 60-mer oligonucleotide probes representing approximately 44,000 unique mouse transcripts, 3) produced web-based ANOVA-FDR software to provide user-friendly microarray data analysis, and 4) developed an algorithm and a fully-automated computational pipeline for transcript assembly from expressed sequences aligned to the mouse genome. In addition, we recently developed a comprehensive database and web browser of the binding sites of transcription factors (TFs) and cis-regulatory modules (CRMs) on the mouse genome (Sharov et al., 2006). These resources and tools are now applied to the systematic analysis of gene regulatory networks in mouse embryonic stem cells. We are currently carrying out a pilot project to test whether it is possible to analyze and identify downstream target genes by monitoring the global gene expression patterns of mouse ES cell lines, where a gene encoding a specific TF is manipulated so that the gene expression can be overexpressed or repressed.